08. Jul 2020

Microliter filter crucible: fast and efficient microplastic analysis

To date there has been no standard method for sampling and analyzing microplastic particle content in the environment. A reliable evaluation of potential risks for humans and the environment is therefore barely possible. Researchers and scientists require standardized and routine procedures for valid inspection results. The solution now comes in the form of a patented microliter filter crucible made of stainless steel, which GKD – GEBR. KUFFERATH AG developed together with the German Federal Institute for Materials Research and Testing (BAM) and the German Federal Environmental Agency (UBA). It facilitates fast and reliable routine analyses for mass content of microplastics in environmental media, even when processing complex samples.

To determine the entry of microplastics into various bodies of water, BAM and UBA use the specially developed thermoanalytical process TED-GC/MS (Thermoextraction Desorption Gas Chromatography Mass Spectrometry). In the case of water or air samples, microplastics are generally detected through filtration of the media. Microplastics from soil samples or sediments need to be concentrated beforehand in a density separation step and the supernatants then need to be filtered out of the solution. Only once they are dry can these samples be transferred to the aluminum oxide crucible of the TED-GC/MS. All of these steps involve the risk of particle loss and contamination if they are not performed using plastic-free equipment in plastic-free ambient conditions. The microliter filter crucible made of stainless steel developed by GKD, BAM, and UBA in the research project RUSEKU, which focuses on representative investigation strategies for an integrative system understanding of specific entry of plastics into the environment, can be used directly for filtration of the sample media or flotation items. This eliminates the need for additional work steps such as the high-risk process of sample transfer and freeze-drying. The risk of particle loss is also minimized. In addition, the microliter filter crucible made completely of stainless steel avoids contamination due to plastic abrasion. As a filter medium, Optimized Dutch Weave from GKD with a geometric pore size of five micrometers is welded onto the base of the ten-millimeter-high container. This robust, single-ply stainless steel mesh guarantees secure retention of all particles above the separating limit of five micrometers while allowing an unusually high flow rate. Together with the filter cake, the non-leak microliter filter crucible made of stainless steel is automatically inserted into the TGA of the TED-GC/MS. It provides a long-awaited solution for routine analysis for industry, research, and regulatory authorities. This innovative measuring crucible has been proving its worth for a year in the analysis of microplastics in mineral water from PET bottles and in quality controls in water-based drinks. Yet its broad scope for use also makes it possible to perform inspections of treated wastewater or surface water in the quality control of various purification processes as well as the analysis of organic fertilizers, soils, or sediments.